TYPO3 Extbase TCA MM-relation filter results by site-defined constant "newRecordStoragePid" - typo3

Question

TLDR:
I've got two models with MM-Relations with different StoragePids defined via Constants in my template.
I don't know how to filter results while querying my data regarding my configured storagePids for my related Model.
Long version:
In my multisite-TYPO3 installation I've got two models "Person" and "PersonalInformation". These models have a MM-Relation defined via TCA.
"Person" contains all general data, stored in a global RecordStore. "PersonalInformation" contains editable Data i.e. images to be editable for each site separately. These data are stored in seperate RecordStores under each site.
That means within each site-template->Constants I've defined the extension-storagePid i.e.: $plugin.tx_myext.persistence.storagePid = 1
This config is on all sites the same, to be able to access the same RecordStore from each Site.
The RecordStore for "PersonalInformation" should be different for each site. So my setup.txt of my extension looks like:
persistence {
storagePid = {$plugin.tx_myext.persistence.storagePid},
{$plugin.tx_tx_myext.persistence.personalInformationStoragePid}
classes {
TYPO3\T3myext\Domain\Model\PersonalInformation {
newRecordStoragePid = {$plugin.tx_myext.persistence.personalInformationStoragePid}
}
}
}
And in my root-site-template under Constants I've defined plugin.tx_myext.persistence.personalInformationStoragePid for each site individually.
My TCA MM-Relation defined for PersonalInformation:
'person' => array(
'exclude' => 1,
'label' => 'LLL:EXT:myext/Resources/Private/Language/locallang_db.xlf:tx_myext_domain_model_person',
'config' => array(
'type' => 'select',
'renderType' => 'selectMultipleSideBySide',
'foreign_table' => 'tx_myext_domain_model_person',
'foreign_table_where' => 'AND 1=1 ORDER BY last_name ASC',
'MM' => 'tx_myext_person_personalinformation_mm',
'size' => 10,
'autoSizeMax' => 30,
'maxitems' => 1,
'minitems' => 0,
'multiple' => 0,
),
),
My TCA MM-Relation defined for Person:
'personalinformation' => array(
'exclude' => 1,
'label' => 'LLL:EXT:myext/Resources/Private/Language/locallang_db.xlf:tx_myext_domain_model_person.personalinformation',
'config' => array(
'type' => 'none',
'readonly' => 1,
'foreign_table' => 'tx_myext_domain_model_personalinformation',
'MM_opposite_field' => 'personalinformation',
'MM' => 'tx_myext_person_personalinformation_mm',
'foreign_table_where' => 'AND tx_myext_domain_model_personalinformation.pid=###The-PID-defined-in-my-site-Const-for-personalInformationStoragePid###'
),
),
If I var_dump my Person in the Frontend all Person.PersonaInformation of all RecordStores are displayed. But I what to show only PersonalInformation Records of the current Site.

Answer 1

The field in the model will always give back all relations, independent of the storage pid. The foreign_table_where in TCA is only for the backend, so this will do nothing for the frontend.
If you want to only get relations from a certain pid, there are several solutions:
Filter it yourself, either in your template, model or controller. Just loop through the relations and check the pid. This option is easiest, but will be slow if you have a lot of relations.
Select the PersonalInformation records separately in your controller using a PersonalInformationRepository with a findByPerson function. This will respect the storagePid set in TypoScript. This will work fine if you only need the information for 1 person. If you need it for multiple persons on 1 page (in a list view for example) you can do this in a custom getPersonalInformation function in your Person model. If it's not cached it could also be slow for lists (depending on the amount of records).
Use a completely custom query using QueryBuilder (https://docs.typo3.org/typo3cms/CoreApiReference/latest/ApiOverview/Database/QueryBuilder/Index.html). This way you can do it in 1 query with joins.
What is the best solution depends on your exact situation and the number of records.